This invention relates in general to vehicle drum brake assemblies and in particular to an improved damped brake shoe support device for use in such a vehicle drum brake assembly.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies can be actuated by hydraulic, pneumatic, or mechanical pressure generated by an operator of the vehicle depressing a foot pedal, pulling a hand lever, and the like. The structure and operation of both drum brake assemblies and disc brake assemblies, as well as the actuators therefor, are well known in the art.
A typical drum brake assembly includes a backing plate which is secured to a fixed, non-rotatable component of the vehicle, such as the vehicle axle housing. A pair of opposed arcuate brake shoes are supported on the backing plate for selective movement relative thereto. Each of the brake shoes has a friction pad or lining secured thereto. The drum brake assembly further includes a hollow cylindrical brake drum which is secured to the vehicle wheel for rotation therewith. The hollow interior of the brake drum defines an inner cylindrical braking surface. The brake drum is disposed adjacent to the backing plate such that the brake shoes extend within the cylindrical braking surface. To effect braking action, the brake shoes are moved outwardly apart from one another such that the friction pads frictionally engage the cylindrical braking surface of the brake drum. Such frictional engagement causes slowing or stopping of the rotational movement of the brake drum and, therefore, the wheel of the vehicle in a controlled manner.
One or more actuating mechanisms are provided in the drum brake assembly for selectively moving the brake shoes outwardly apart from one another into frictional engagement with the cylindrical braking surface of the brake drum. Usually, a hydraulically or pneumatically actuated service brake mechanism is provided for selectively actuating the drum brake assembly under normal operating conditions. Such a service brake mechanism can include a hydraulic cylinder having a pair of opposed pistons which abut and move the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum. A mechanically actuated parking and emergency brake mechanism is also usually provided for selectively actuating the drum brake assembly. The parking and service brake mechanism can include an actuating lever pivotally supported on one of the brake shoes. The actuating lever is connected to a cable which, when pulled, moves the brake shoes apart from one another into frictional engagement with the cylindrical braking surface of the brake drum.
This invention relates to an improved drum brake assembly having at least one damped brake shoe support device secured to an associated backing plate which is effective to reduce brake noise during actuation of the drum brake assembly. The drum brake assembly includes a backing plate supported relative to a vehicle component, at least one brake shoe supported on the backing plate for selective movement into frictional engagement with a brake drum, a brake mechanism for selectively moving the brake shoe into frictional engagement with the brake drum, and at least one damped brake shoe support device carried by the backing plate. The damped brake shoe support device includes a first member and a second member. The first member is formed of a relatively rigid material and includes a first end which defines a sliding surface for engagement with an adjacent surface of a brake shoe sliding surface. The second member is formed of a damping material and is interposed between the first end of the first member and the backing plate. As a result, the damped brake shoe support device of the present invention results in a reduction of brake noise generated during braking due to the vibration damping provided thereby.
Other advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.